The overall objective of this research project is to determine rates of production and utilization of selected blood-borne metabolites in normal, fasting, and disease humans by means of isotope tracer techniques. Glucose, free fatty acids and the ketone bodies are the principal metabolites of interest because of their major contribution as fuels for caloric homeostasis. Currently, our major research efforts are devoted to studies of acetone metabolism during starvation induced and diabetic ketosis.